I think the Moto X falls into the "pure Android experience" category. Plus one. Well plus many. The overall feel is basically stock android. However, they really added great functionality to the phone such as touchless control, Active display, moto assist, quick capture and more. It really snappy and smooth, I would say it beats the nexus 4. Even if its "last years" chipsets, Motorola's 8x chip is especially optimized for the phone to carry out these functions and saves battery. Also, the battery life is amazing. Most say it can last a day and maybe more but ofcourse your mileage will vary.
Now for some "downsides" or i would say Tradeoffs.
In order for that amazing battery life and active display to work it, it has a 720P Amoled display. As it looks great, if it is compared to today's 1080P's screens (which the nexus 5 is "confirmed?" to have) then you'll see the difference. Also it has a S4 pro processor compared to Nexus 5's Snapdragon 800's with Adreno 330. And 4.7 inch vs 5 inch (4.97 something something). The moto x has such a comfortable design that makes it easy to hold.
(btw I don't own a moto x, my close friend does)
Now as which phone to have? Well, if you can wait a couple weeks, then Nexussss 555555555 alllll thheeeee wayyyyyyy, not sure about all those sold outs because we dont even know when the announce date is! but the nexus 7 2013 shipping went pretty smooth. People received it within 2-3 business days. hopefully the same results for the Nexus BUT again We dont even know when it is release. So you MAY wait a week, a month or maybe just a DAY, we dont know. So if your current phone can hold out for ATLEAST 2 more months (hopefully not that long of a wait) then I say wait for Nexus 5
but if youre itching for a new phone and tired of Google's teasing. then the Moto X it is plus you get to customizing but i don't think you are going to do so in this situation. you would not go wrong with it. Unless you're one of those "top of line Specs is everything and I must have the latest and greatest" people. Also If you can, check the moto x out first, see if you can bare the "tradeoffs" and love the functionality.
I would buy the moto x IF Tmobile had moto maker and was on a EIP plan... (high school student, sadly)
Also the Nexus 5 is cheaper. forgot to mention lol. For 16gb its 349 and HOPEFULLY 399 for the 32g ..